Implementation of multiple simultaneous calls in a mobile communication system

ABSTRACT

In an implementation of multiple simultaneous calls for a mobile station in a mobile communication system, a common traffic channel is allocated to several simultaneous calls of the mobile station, so that the calls share capacity of the common channel. Logical links are established for each call inside a common radio link protocol or link access control protocol, established over the common traffic channel between the mobile station and an interworking function. The common traffic channel is allocated when the first call or calls are set up, and the capacity of the traffic channel is adjusted dynamically during the calls. The common traffic channel capacity is increased or the allocated capacity is reallocated when a new call is added to the traffic channel. Correspondingly, the capacity is decreased or reallocated when a call is cleared from the common traffic channel.

FIELD OF THE INVENTION

The invention generally relates to mobile communication systems andparticularly to multiple simultaneous calls in a mobile communicationsystem.

BACKGROUND OF THE INVENTION

In addition to conventional speech transmission, modern mobilecommunication systems offer various data transmission services tosubscribers. The services of mobile communication systems are generallyclassified into tele-services and bearer services. A bearer service is atelecommunications service which provides signal transmission betweenthe user interfaces and the network interfaces. An example of bearerservices is a modem service. In the tele-service terminal services arealso offered by the network. Important tele-services include speech,telefax and videotex services. The bearer services are usuallysubdivided into groups, such as asynchronous bearer services andsynchronous bearer services, on the basis of a certain feature. In thecase of the asynchronous bearer service the transmitting terminal andthe receiving terminal are able to maintain their synchronization onlyfor each single character to be transmitted. In the case of thesynchronous bearer service the transmitting terminal and the receivingterminal are synchronized with each other for the whole duration of datatransmission. Each such bearer service group comprises a number ofbearer services, such as a transparent service and a non-transparentservice. In the transparent service the data to be transmitted isunstructured and transmission errors are corrected only by means ofchannel coding. In the non-transparent service the data to betransmitted is structured into protocol data units (PDU) andtransmission errors are corrected using retransmission protocols (inaddition to channel coding).

Calls have traditionally been calls with one service (one connection),i.e. each call has been clearly e.g. a speech call or a data call of acertain type and optimized for a certain service. Multimedia calls whichsimultaneously support various types of information transmission orservices, such as video, speech, file transfer, have recently beenintroduced in fixed data networks, particularly in the Internet.

Existing mobile communication systems do not offer any special bearerservices for multimedia calls or for simultaneous use of multiple dataservices. There is only one traffic channel available for a data call,the channel being either transparent (T) or non-transparent (NT).Depending on the required transmission rate a traffic channel mayconsist of one sub-channel (e.g. TDMA time slot) or several sub-channels(e.g. several TDMA time slots for high-speed data transmission, such asHSCSD in the GSM system). Any shared use of the traffic channel has tobe implemented on the application layer, i.e. in the end user'sapplications. Time-critical multimedia calls, e.g. video phoning, haveto use transparent circuit-switched bearer services because other dataservices cannot guarantee as small variation of the transmission delayas the video service requires. Too long a transmission delay causesvisible interference in the video picture at the receiving end.Applications which are not time-critical and require accuratetransmission usually use non-transparent bearer services. An example ofsuch an application is transfer of data files.

As was stated above, the problem related to the present mobilecommunication systems is that they either provide a transparent or non-transparent traffic channel or a packet service (such as GPRS, GeneralPacket Radio Service) for a multimedia call between two mobile stationsor between a mobile station and a terminal or server in a fixedcommunication network. Packet radio services and the non-transparenttraffic channel are not suitable for video phoning or othertime-critical applications. On the application layer the transparentbearer service requires an error correction protocol which is usuallynot optimized for a radio connection. This means that a multiserviceand/or multimedia channel has to always use a transparent bearer serviceand perform multiplexing and error correction on the application layerin the end users' terminals.

In the future it will be required of the mobile communication systems,particularly of the 3^(rd) generation systems, such as UMTS (UniversalMobile Telecommunications Systems) that the mobile communication networkand mobile station should support several simultaneous calls between themobile station and several other parties at different destinations. Thecalls may be traditional calls with one connection or above-describedmultimedia calls or calls with multiple connections. It is also requiredthat it should be possible to add or drop different connections or callsindependently of one another.

The key factor in the design and implementation of mobile communicationnetworks is the effective utilization of the radio spectrum. Multiplecalls should also be implemented by making the maximum use of thechannel capacity. Control of multiple calls, e.g. handover, should be assimple as possible both for the mobile communication system and themobile station.

DISCLOSURE OF THE INVENTION

One of the objectives of the invention is to meet the above- mentionedrequirements, particularly the effective utilization of the availablechannel capacity and simple handover procedure of multiple simultaneouscalls.

This is achieved with a method of providing two or more simultaneousdata calls for one mobile station in a mobile communication system. Themethod is characterized by the following steps of

-   -   assigning only one common traffic channel to two or more        simultaneous calls of a mobile station, and    -   sharing the capacity of the traffic channel between the        simultaneous calls.

The invention also relates to a mobile station according to claim 13 andto a mobile communication network according to claim 19.

According to the basic idea of the invention, one common traffic channelis reserved for several or all simultaneous calls of a mobile station,and the capacity of the channel is shared between the calls. Here theterm traffic channel refers both to a single channel and to a set of twoor more parallel sub-channels used in high-speed multichannel datatransmission (e.g. the HSCSD channel of the GSM system). The term callmeans both a traditional call with one connection and a multimedia callor a multiple connection call. The traffic channel is reserved when thefirst call or calls are being set up. If several calls are set upsimultaneously, the capacity of this one common traffic channel isdetermined by the combined (total) capacity requirement of the differentcalls. In the preferred embodiment of the invention the capacity of thetraffic channel is adjusted dynamically. The capacity of a trafficchannel which is already allocated to one or more ongoing calls isincreased or the allocated capacity is reallocated when a new call or anew connection of an old call is added to the traffic channel.Correspondingly, the capacity is reduced or the allocated capacity isreallocated when a call or a connection of a call is cleared (dropped)from a traffic channel. The traffic channel is released after the lastcall has been cleared.

The calls may be non-transparent calls (NT), transparent calls (T) ormultimedia calls which contain both NT and T connections. Thus thetransparent connection of the multimedia call can be used fortransmitting time-critical information which does not allow-the use ofan error correction protocol based on retransmission, and thenon-transparent connection can be used for transmitting lesstime-critical information which allows error correction based onretransmission. Thus the invention enables implementation ofmultiservice calls through the traditional traffic channel of the mobilecommunication network. The necessary multiplexing and demultiplexing canbe carried out in the terminals and interworking functions of the mobilecommunication network. Thus these functions do not need to be performedon the application layer by the end user like in prior art solutions.

In an embodiment of the invention NT calls, T calls and separate T or NTconnections use logical links inside a common radio link protocol (RLP)or link access control protocol (LAC), which is established between themobile station and the interworking function.

The call may also be a packet-switched call, in which case packet-switched traffic is transmitted over the same traffic channel withcircuit- switched traffic. The packet-switched traffic preferably sharesthe traffic channel capacity available for NT traffic. The packets aretransmitted e.g. interleaved with RLP or LAC protocol frames orencapsulated in the protocol frames.

According to another embodiment of the invention, if the mobilecommunication network is temporarily unable to allocate moretransmission capacity or the required amount of capacity when a new callor connection is established, the available capacity is reallocated tothe calls. The mobile communication network allocates the requestedcapacity later when capacity becomes available in the network.

According to still another embodiment, the mobile station and/or thenetwork monitor(s) the traffic of at least one call or connection, andif there is temporarily no data traffic in the call or connection, ittemporarily uses the free resources for the traffic of another call(calls) or connection (connections). Thanks to this all capacity that isfree in the traffic channel can be utilized to the maximum extent everymoment.

The invention optimizes the use (utilization) of the traffic channelcapacity compared to a case in which separate simultaneous calls of amobile station use different traffic channels. In the case ofcongestion, i.e. during the traffic peaks, the mobile communicationnetwork can support a higher number of calls with the same amount ofavailable traffic channel capacity. The traffic channel capacity can beadjusted dynamically and allocated depending on the number of calls andtheir requirements. Control of simultaneous calls is simpler. Forexample, handover of several calls is simple to implement both inrespect of the mobile communication network and the mobile stationbecause only one traffic channel needs to be handed over. Consequently,traditional handover procedures can be applied as such, which is anadvantage particularly when multicall service is introduced intoexisting mobile communication systems.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the preferred embodiments of the invention will bedescribed with reference to the accompanying drawings, in which

FIG. 1 illustrates a GSM mobile communication system,

FIG. 2 illustrates protocols and functions that are needed in non-transparent bearer services of the GSM system,

FIG. 3 illustrates a system configuration where several simultaneouscircuit-switched calls of the same mobile station MS can be implementedin the GSM environment,

FIG. 4 illustrates a more detailed equipment configuration which allowsimplementation of several simultaneous circuit-switched calls of thesame mobile station MS in the GSM environment inside a common RLP/LAClink,

FIG. 5 illustrates an RLP/LAC frame which includes a virtual channelidentifier,

FIG. 6 graphically illustrates virtual channels inside a common trafficchannel in the embodiment of FIG. 4,

FIG. 7 illustrates a system configuration where simultaneouscircuit-switched and packet-switched calls of the same mobile station MScan be implemented in the GSM environment,

FIG. 8 illustrates transmission of interleaved packet data frames andLAC frames via the common traffic channel,

FIG. 9 illustrates a system configuration where simultaneouscircuit-switched and packet-switched calls of the same mobile station MScan be implemented in a 3^(rd) generation radio access system, such asUMTS,

FIG. 10 is a more detailed block diagram of the system configurationillustrated in FIG. 9,

FIG. 11 illustrates a system configuration where simultaneouscircuit-switched and packet-switched calls of the same mobile station MScan be implemented in a pure 3^(rd) generation radio access system,where IWU-A and MSC/IWF have been integrated together,

FIG. 12 illustrates a system configuration where parts of a 3^(rd)generation system, such as the LAC protocol, are integrated into theMC/IWF of the 2^(nd) generation, and

FIG. 13 is a block diagram of a mobile services switching centre whichcomprises an integrated IWF pool supporting the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is applicable to all digital wirelesstelecommunications systems, such as cellular systems, WLL (WirelessLocal Loop) and RLL (Radio Local Loop) networks, satellite-based mobilecommunication systems, etc. Here the term mobile communication system(or network) generally refers to all wireless telecommunicationssystems. There are several multiple access modulation techniques whichfacilitate traffic involving a large number of mobile users. Thesetechniques include time division multiple access (TDMA), code divisionmultiple access (CDMA) and frequency division multiple access (FDMA).The physical concept of the traffic channel varies in different multipleaccess methods, being primarily defined by means of a time slot in TDMAsystems, by means of a spreading code in CDMA systems, by means of aradio channel in FDMA systems, by means of a combination of these, etc.In modern mobile communication systems it is possible to allocate a setof two or more basic-rate traffic channels (sub- channels), i.e. ahigh-speed traffic channel, to a mobile station for high-speed datatransmission. Here the term traffic channel refers both to a singlebasic- rate traffic channel and to a high-speed traffic channelconsisting of two or more basic-rate traffic channels. The basic idea ofthe present invention is independent of the type of the traffic channeland the multiple access method used.

The present invention is particularly suitable for data transmissionapplications in the 3^(rd) generation mobile communication systems, suchas UMTS, in digital GSM mobile communication systems (Global System forMobile Communications) and in other GSM-based systems, such as DSC1800(Digital Communication System), in the US digital cellular system PCS(Personal Communication System) and in WLL systems which are based onthe above-mentioned systems. The invention will be described below usingthe GSM mobile communication system as an example. The structure andfunction of the GSM system are very familiar to a person skilled in theart and they are defined in the GSM specifications of ETSI (EuropeanTelecommunications Standards Institute). Reference is also made to GSMSystem for Mobile Communication, M. Mouly and M. Pautet, Palaiseau,France, 1992; ISBN: 2-9507190-0-7.

The basic structure of the GSM system is illustrated in FIG. 1. The GSMsystem consists of two parts: a base station system BSS and a networksubsystem NSS. The BSS and mobile stations MS communicate over radioconnections. In the base station system BSS each cell is served by abase transceiver station BTS. A number of base transceiver stations areconnected to a base station controller BSC, which controls the radiofrequencies and channels the BTS uses. The BSCs are connected to amobile services switching centre MSC. Certain MSCs are connected toother telecommunications networks, such as the public switched telephonenetwork PSTN, and comprise gateway functions for calls transmitted tothose networks and calls arriving from those networks. These MSCs areknown as gateway MSCs (GMSC). There are also at least two databases, ahome location register HLR and a visitor location register VLR.

The mobile communication system comprises adaptation functions foradapting the internal data connection of the mobile communicationnetwork to the protocols used by the terminals and othertelecommunications networks. The adaptation functions typically includea terminal adaptation function TAF on the interface between the mobilestation and the data terminal connected to the mobile station and aninterworking function IWF on the interface between the mobile stationand another telecommunications network, typically in association withthe mobile services switching centre. Usually the mobile servicesswitching centre comprises various kinds of adapter equipment pools forsupporting different data services and data protocols, such as a modempool which comprises modems and telefax adapters for modem and telefaxservices, UDI/RDI rate adapter pool, etc. Referring to FIG. 1, in theGSM system a data connection is established between the terminaladaptation function TAF 31 of the mobile station MS and the interworkingfunction IWF 41 in the mobile communication network. In the case of datatransmission in the GSM system this connection is an UDI coded digitalfull duplex connection adapted to V.24 interfaces. In non-transparentdata services the GSM connection also uses a radio link protocol RLP.The TAF adapts the data terminal equipment DTE connected to the mobilestation MS to said GSM data connection, which is established over aphysical connection using one or more traffic channels. The IWF connectsthe GSM data connection to a V.110 or V.120 network, such as an ISDNnetwork or another GSM network, or to another transit network, such asthe public switched telephone network PSTN. The CCITT recommendation fora V.120 rate-adapted connection is disclosed in the publication CCITTWhite Book: V.120.

As was explained above, modern mobile communication systems supportdifferent tele-services and bearer services. The bearer services of theGSM system are defined in the GSM specification 02.02 and thetele-services in the GSM specification 02.03.

FIG. 2 illustrates protocols and functions which are needed in the IWF(either in the MSC or in a WLL-specific network element) for non-transparent bearer services. The non-transparent circuit-switchedconnection over the GSM traffic channel between the terminal adaptationfunction TAF and the interworking function IWF comprises severalprotocol layers which are common to all these services. These includevarious rate adaptation functions RA, such as RA1′ between the terminaladaptation function TAF and the CCU unit (Channel Codec Unit) located inthe base station system BSS, RA1 between the CCU unit and theinterworking function IWF, RAA between the CCU unit and a transcoderunit TRAU located remote from the base station, and RA2 between thetranscoder unit TRAU and the interworking function IWF. Rate adaptationfunctions RA are defined in GSM recommendations 04.21 and 08.20. Trafficbetween the CCU unit and the transcoder unit TRAU is defined in the GSMrecommendation 08.60. At the radio interface the RA1′ rate-adaptedinformation has also been channel-coded according to the GSMrecommendation 5.03, which is illustrated by the FEC blocks in themobile station MS and CCU unit. The IWF and TAF also comprise protocolsof upper layers which are service-specific. In the asynchronousnon-transparent bearer service the L2R (Layer 2 Relay) and RLP (RadioLink Protocol) protocols and a modem or a rate adaptation function inthe direction towards the fixed network are needed in the IWF. L2Rfunctionality for non-transparent character-oriented protocols isdefined e.g. in the GSM recommendation 07.02. The RLP protocol isdefined in the GSM recommendation 04.22. The RLP is a frame-structured,balanced (HDLC type) data transmission protocol in which errorcorrection is based on retransmission of corrupted frames at the requestof the receiving party. The interface between the IWF and e.g. theaudiomodem MODEM is in accordance with CCITT V.24. In FIG. 2 thisinterface is indicated with symbol L2. This non-transparentconfiguration is also used in connection with access to the Internetnetwork.

The protocol structure of the transparent bearer service and GSM telefaxservice is very similar to that illustrated in FIG. 2, except that theL2R/RLP function has been replaced with another function. In anasynchronous transparent bearer service the IWF needs asynchronous-synchronous conversion RA0 and a modem or a rate adaptation function inthe direction towards the fixed network. In the telefax service the IWFneeds GSM telefax protocol functions and a modem. The telefax connectionis also transparent. The GSM telefax service is defined in the GSMrecommendation 03.45.

In the HSCSD concept of the GSM system a high-speed data signal issplitted into separate data flows which are then transmitted via Nsubchannels (N traffic channel time slots) on the radio interface. Afterthe data flows have been splitted, they are carried on subchannels as ifthey were independent of one another until they are combined again inthe IWF or MS. However, logically these N subtraffic channels belong tothe same HSCSD connection, i.e. they form one HSCSD traffic channel.According to the GSM recommendations, data flows are splitted andcombined in a modified RLP, which is thus common to all subchannels.Below this common RLP each subchannel has the same protocol stackRA1′-FEC-FEC-RA1′-RAA-RAA-RA2- RA2-RA1 between the MSFTAF and theMSC/IWF, the protocol stack being illustrated for one traffic channel inFIG. 2. Thus the HSCSD traffic channel according to the GSMrecommendations will still use the common RLP for different subchannels,even though the bit rate of an individual subchannel may be up to 64kbits/s.

As was stated above, solutions are being developed for the GSM systemwhich enable data rates up to 64 kbits/s per time slot or data ratesexceeding 64 kbits/s in the multi-slot constellation (HSCSD). However,this development work does not affect the protocol structures describedabove, but only the bit rate of the HSCSD traffic channel. Thus theHSCSD traffic channel according to the GSM recommendations will stilluse the common RLP for different subchannels, even though the bit rateof an individual subchannel may be up to 64 kbits/s and the total rateof the HSCSD traffic channel n*64 kbit/s.

As was explained above, in the future it will be required of the mobilecommunication systems, particularly of the 3^(rd) generation systems,such as UMTS (Universal Mobile Telecommunications Systems) that themobile communication network and the mobile station should supportseveral simultaneous calls between the mobile station and several otherparties at different destinations. The calls may be traditional callswith one connection or multimedia calls or calls with severalconnections. It is also required that it should be possible to add ordrop separate connections or calls independently of one another. Thechannel capacity should be utilized as efficiently as possible. Inaddition, control of multiple calls, such as handover, should be assimple as possible both for the mobile communication system and themobile station.

According to the basic idea of the invention one common traffic channelis allocated to several or all simultaneous calls of the same mobilestation and the capacity of the channel is shared between the calls.

FIG. 3 illustrates by way of example how several simultaneouscircuit-switched calls of the same mobile station can be implemented inthe GSM environment. There are n active applications in the terminal TEof the mobile station MS, and each of the different applicationsrequires one call or one connection of a multimedia call. One trafficchannel has been established between the mobile station MS and theinterworking function IWF, the channel being common to all calls. Avirtual connection (circuit) is established for each call or connectionof a call inside the common traffic channel and each virtual connectionuses part of the traffic channel's capacity. The MS connects eachapplication to its respective virtual connection in the traffic channel.The interworking function IWF connects the virtual connections of thetraffic channel to separate physical fixed network channels. One suchfixed network channel is established between the terminals TE of thefixed network (e.g. PSTN or ISDN) and the interworking function IWF foreach call. The fixed network channel may also comprise severalconnections (multimedia call).

The calls may be for example non-transparent calls (NT), transparentcalls (T) or multimedia calls which comprise both NT and T connections.Furthermore, one or more calls may be packet-switched.

The capacity of the common traffic channel can be allocated to the callse.g. by allocating specific information bits transmitted through thetraffic channel to each call or connection of a call. In the GSM system,for example, V.110 frames are transmitted between the rate adaptationfunction RA1′ and the rate adaptation function RA1. A specific number ofthe data bits of these frames may be reserved for each call.

In the preferred embodiment of the invention NT calls, T calls andseparate T or NT connections use logical links inside a common radiolink protocol (RLP) or link access control protocol (LAC) which isestablished through the traffic channel between the mobile station MSand the interworking function IWF (or IWU-A).

FIGS. 4 and 6 illustrate such data transmission configuration for purecircuit-switched applications in the GSM environment.

Referring to FIG. 4, the terminal TE (such as a personal computer) ofthe mobile station MS comprises a number of applications 1 . . . n, someof the applications requiring transparent calls (T) and somenon-transparent calls (NT). The applications 1 . . . n are connected tothe radio terminal part MT of the mobile station MS through anapplication interface, such as Mobile API/MEXE (Mobile ApplicationProgramming Interface/Mobile Execution Environment). The MT comprises anRPL/LAC unit 51, which supports the radio link protocol RLP or anothersuitable link access control protocol LAC. The RLP/LAC unit 51 comprisestwo functional parts, i.e. a control unit 510 and a retransmissionmechanism 511. The control unit 510 performs all functions related tothe RLP/LAC protocol, including framing, timing, buffering of data,allocation of virtual channels, multiplexing/demultiplexing of differentcalls to the virtual channels of the common traffic channel, and controlof RLP/LAC protocol functions. Only functions and mechanisms related toretransmission have been transferred to the unit 511. Applicationsrequiring a transparent (T) connection or call have been directlyconnected to the unit 510, whereas applications requiring anon-transparent (NT) call or connection have been connected to the unit510 via the retransmission unit 511. This allows to transmit bothtransparent and non-transparent connections inside the common RLP/LAClink in one GSM traffic channel.

Referring further to FIG. 4, the interworking function IWF, which ispreferably located in the mobile services switching centre MSC,comprises an RLP/LAC unit 52, which corresponds to the unit 51 in themobile station MS. In other words, the RLP/LAC unit 52 comprises acontrol unit 520 and retransmission mechanism 521, which have the samefunctionality as the respective units 510 and 511 in the mobile stationMS. The I/O ports of the unit 520 (which are intended for transmittingand receiving transparent (T) data to and from the fixed network (PSTN,ISDN)) are connected to a switching unit 53, which may connect each portselectively to a rate adaptation unit RA 54, modem 55 or telefaxprotocol adapter FAX 56, for example. Units 54, 55 and 56 are connectedto other telecommunications networks, such as PSTN or ISDN.Correspondingly, the ports of the unit 521 (which are intended fortransmitting and receiving non-transparent data to and from anothertelecommunications network) are connected to the switching unit 53,which can selectively connect the ports to units 54 to 56 according tothe service a given call requires. Thanks to the IWF according to FIG. 4different calls or connections (one in each port of the unit 520 or 521)can thus be connected selectively and independently of other calls to aseparate individual physical channel in another telecommunicationsnetwork. Alternatively, it may be advantageous in some situations toconnect two calls or connections to the same physical channel in anothertelecommunications network, e.g. when the calls have the samedestination.

One common traffic channel is allocated between the mobile station MSand the interworking function IWF when the first call or calls are setup. If several calls are set up simultaneously, the capacity of thecommon traffic channel is determined by the combined (total) capacityrequirement of the different calls.

In normal GSM call set-up the MSC receives a BCIE element (BearerCapability Element) in the set-up message from the mobile station (orfrom the subscriber database or another switching centre). The BCIEelement includes information on the call type as well as on the bearerservices and the protocol the call requires. On the basis of thisinformation the MSC can select and initialize the IWF equipment suitablefor the call in question. In an embodiment of the invention the BCIEelement can be provided with a new parameter or parameter value whichenables the MSC to choose the IWF equipment supporting the functionalityof the invention for the call.

When the common traffic channel is established, an RLP/LAC protocol linkis established between the RLP/LAC units 51 and 52 in the manner definedfor the RLP/LAC protocol, e.g. according to the RLP protocol in the GSMmobile communication system. In the preferred embodiment of theinvention the RLP/LAC units also negotiate with each other about theestablishment of virtual channels (circuits) inside the common RLP/LACprotocol link by means of internal signalling of the traffic channel. Inthe GSM system, for example, this inband negotiation may be implementedby means of the XID mechanism and XID frames of the radio link protocolRLP, which are normally used for signalling through a non-transparentconnection. The logical subchannels (circuits) can be established e.g.by determining logical channel identifiers inside the information fieldof the RLP/LAC frames, for instance. FIG. 5 illustrates an RLP/LAC frameprovided with a logical channel identifier. The frame comprises a header(H), information field and frame check sequence FCS. The virtual channelidentifier VCI of the invention is located at the beginning of theinformation field. The VCI preferably consists of a call identifier(which distinguishes calls from one another) and a connection identifier(which distinguishes the connections of a call from one another). Suchuse of several logical channels allows to run several point-to-pointservice sessions simultaneously through one RLP/LAC connection.

The above-mentioned inband negotiation process may be for example thefollowing kind of process. When a common RLP/LAC link has beenestablished in the common traffic channel, the RLP/LAC unit 51 sends aXID frame including a suggestion for a certain virtual channelallocation to the RPL/LAC unit 52. If necessary, the unit 51acknowledges with a XID frame, after which the units 51 and 52 start tomultiplex calls to subchannels in the negotiated manner. Allocation ofsubchannels comprises both allocation of subchannel identifiers VCI andallocation of a certain amount of channel capacity to each virtualchannel. In the mobile station the unit 51 links each virtual channelwith the corresponding application (call). Correspondingly, in theinterworking function IWF the RLP/LAC unit 52 and switching unit 53provide coupling of the virtual channels to the separate physicalchannels in another telecommunications network. Alternatively, it isalso possible to include definition of the virtual channel capacity(e.g. bit rate) needed for each call or connection in theabove-mentioned BCIE element or another signalling element. In that casethe capacity of the common traffic channel is allocated in the IWFaccording to this information and no inband negotiation is needed(unless negotiation is needed for another reason).

FIG. 6 is a graphical illustration of four simultaneous calls which havebeen set up via the common traffic channel according to the invention.Five logical channels 61A, 61B, 61C, 61D and 61E are established insidethe common traffic channel and the RLP/LAC link 60. Logical channels61A, 61B and 61E are connected to applications 1, 2 and n, respectively,on the MS side, and correspondingly to physical PSTN/ISDN channels 62,63 and 65 on the IWF side. The call of the application n−1 comprises twoseparate connections, which are connected to logical channels 61C and61D on the MS side. On the IWF side the logical channels 61C and 61D areconnected to a common physical channel 64.

After the multiple call according to the invention has been set up, thecapacity of the common traffic channel can be adjusted dynamically. Thecapacity of a traffic channel to which one or more ongoing calls havebeen allocated is increased or the allocated capacity is reallocatedwhen a new call, or a new connection of an old call, is added to thechannel. When the MS requires one more call, it sends a call set-uprequest to the mobile services switching centre MSC, which changes theconfiguration of the traffic channel so that the total capacitycorresponds to the capacity required by all calls. A correspondingprocedure is carried out when the MS clears a call from the trafficchannel. Increase or decrease of capacity may mean, for example, that 1)more or fewer subchannels or subflows are allocated in multiple channelconfiguration (such as HSCSD), 2) the channel coding is changed in orderto increase or decrease the data rate, 3) the ratio of chip rate to datarate (chip rate over data rate) is changed in the code division multipleaccess system (CDMA), or other means provided by the mobilecommunication system in question are used. After the configuration andcapacity of the common traffic channel have been changed, the RLP/LACunits 51 and 52 negotiate a virtual channel for the new call, delete thevirtual subchannel of the cleared call or possibly negotiate aboutreallocation of the capacity to the calls. A connection can be added ordeleted within an existing call as was described above, or negotiationabout allocation/deallocation of a virtual channel and reallocation ofthe capacity may be carried out only between the units 51 and 52 due tothe addition/deletion of a connection.

Also, if the MS is temporarily unable to allocate more transmissioncapacity to the traffic channel when a new call or connection is beingadded, the RLP/LAC units 51 and 52 perform negotiation, in which case anew virtual channel is established for a new call or connection and theavailable capacity is reallocated.

When the MS sets up a new call or connection in addition to the ongoingones the MSC notices that the MS is already engaged in a data call andreroutes the call/connection to the same IWF element.

Transparent (T) data is packed into RLP/LAC frames, i.e. a virtualchannel is also allocated to T connections in the common trafficchannel. However, retransmission functions are not applied to the Tdata, but an unacknowledged mode transmission because transparent (T)data is supplied directly to the RLP/LAC units 51 and 52 and not via theretransmission mechanism 511, 521. Furthermore, the transmitting RLP/LACunit 51, 52 guarantees that a frame is transmitted to each connection atregular intervals so that a constant (or nearly constant) delay and aconstant rate are kept up.

Transparent calls require a constant capacity, and thus the capacity ofthe transparent calls cannot be reduced when the total capacity of thetraffic channel is inadequate. However, non-transparent calls and packetconnections can be maintained with minimal traffic channel capacityusing flow control, buffering and congestion control at both ends of thetraffic channel, e.g. in the RLP/LAC units 51 and 52.

According to an embodiment of the invention the RLP/LAC units 51 and 52monitor the traffic of transparent (T) calls and connections. If the MS,for example, detects that application 1 transmits fill data according tothe protocol, e.g. flags or control frames, in a transparent call, theRLP/LAC unit 51 does not transmit the fill data to the traffic channel.Instead, the RLP/LAC unit 51 transmits RLP/LAC frames (or packets) ofone or more non-transparent (or packet-switched) connections, i.e.RLP/LAC frames which contain the virtual channel identifier VCI of thenon-transparent connections instead of the VCI of the transparentchannel. At the receiving end the RLP/LAC unit 52 returns the missingprotocol fill data to the transparent data flow, even though the filldata is not transferred via the traffic channel. This may happen e.g. sothat the RLP/LAC unit 52 automatically adds a certain fill to outgoingtransparent data flow when it detects that the traffic channel does notreceive the RLP/LAC frame related to the T connection within apredetermined time from the previous RLP/LAC frame. The units 51 and 52function correspondingly in the opposite transmission directions. Thanksto the additional feature of this invention all free capacity in thetraffic channel is utilized efficiently every moment.

The present invention is also suitable for simultaneous transmission ofcircuit-switched data and packet-switched data. Packet-switched trafficis transmitted on the same channel with the circuit-switched traffic.The packet-switched traffic preferably shares the capacity of thetraffic channel, which is available for NT traffic. Packets aretransmitted e.g. interleaved with RLP or LAC protocol frames orencapsulated in the protocol frames.

FIGS. 7 and 8 illustrate simultaneous transmission of circuit-switcheddata and packet switched-data in the GSM environment. The terminal TE ofthe mobile station comprises data applications 1 . . . n, each of whichrequires a dedicated call or connection. The applications 1 . . . nestablish circuit-switched transparent (T) or non-transparent (NT)connections which are connected to the LAC/RLP unit 51 in the MT part ofthe mobile station MS. The structure and functions of the RLP/LAC unit51 are preferably identical to those of the unit 51 illustrated in FIG.4.

The mobile services switching centre MSC comprises an interworkingfunction IWF which is preferably identical to the interworking functionIWF illustrated in FIG. 4. To be more precise, the IWF comprises anRLP/LAC unit 52, switching unit 53 and rate adaptation function RA 54,modem and telefax unit 56, which are connected to physical channels inanother telecommunications network, such as PSTN or ISDN. The RLP/LACunit 51 and the interworking function IWF establish an RLP/LAC linkbetween themselves via the common traffic channel. The RLP/LAC linkcomprises virtual channels for each call or connection, as was describedabove with reference to FIGS. 4, 5 and 6. Circuit-switched data istransferred between the unit 51 and the IWF in RLP/LAC frames.

Referring further to FIG. 7, the application n (or alternatively severaldata applications) is a packet data application which requires a packetdata call in a packet data network. In the embodiment illustrated inFIG. 7 packet data frames are transmitted interleaved with the RLP/LACframes in the common traffic channel. For this purpose the packet dataframes produced by the application N and the RLP/LAC frames produced bythe unit 51 are supplied to a multiplexing and demultiplexing unit 71,which multiplexes the LAC frames and packet data frames to the commontraffic channel in proportion to the transmission channel capacityallocated to them. There is a corresponding multiplexing anddemultiplexing device 72 in the mobile services switching centre MSC,which demultiplexes the RLP/LAC frames from packet data frames. TheRLP/LAC frames are supplied to the interworking function IWF. The packetdata frames are supplied to a packet data node or packet data handlerPDN, which transmits them further to the packet network. Multiplexing ofthe LAC frames and packet data frames, their interleaved transmission onthe common traffic channel and demultiplexing according to the inventionare illustrated graphically in FIG. 8. Transmission of packet data andcircuit-switched data occurs in the same way in the opposite directionMSC-MS.

FIG. 9 illustrates how several simultaneous circuit-switched andpacket-switched calls of the same mobile station MS may be implementedin the third generation radio access network, e.g. UMTS. The radioaccess network is connected to core networks by means of an interworkingfunction unit or units IWU-A (add-on unit). In this example the mobilecommunication network and the packet network are located in the corenetworks. The terminal TE of the mobile station MS comprises n activeapplications, each of which requires one call or one connection of amultimedia call. One traffic channel which is common to all calls isestablished between the mobile station MS and the network adapter IWU-Aas well as between the interworking functions IWU-A and IWF. A virtualconnection (circuit) is established for each call or connection of acall inside the common traffic channel, each virtual connection using aspecific part of the traffic channel's capacity. The IWU-A connectspacket-switched calls to the packet data node PDN. Data packets aretransmitted between the PDN and the packet data terminal TE via apacket- switched packet network. The IWU-A connects circuit-switchedcalls to the interworking function IWF. The interworking function IFWconnects the virtual connections of the traffic channel to separatephysical channels in the fixed network. There is one physical channelper each circuit-switched call between the fixed network terminals TE(e.g. PSTN or ISDN) and the interworking function IWF.

FIG. 10 illustrates the system of FIG. 9 in greater detail, the mobileservices switching centre MSC and interworking function IWF of thesystem being of the GSM type. The mobile station MS comprises three dataapplications 1, 2 and 3, the first one of which transmits transparentcircuit-switched data, the second one non-transparent circuit-switcheddata and the third one packet-switched data. The MS also comprises anLAC unit 91, which supports a link access control protocol LAC of athird generation mobile communication system. The first interworkingfunction IWU-A comprises a corresponding LAC unit 92. A traffic channelof the radio access system and an LAC link is established between theLAC unit 91 and the LAC unit 92 according to the principles describedwith reference to FIG. 4. Virtual channels are allocated inside the LAClink (three channels in this case). The LAC unit 91 encapsulates thecircuit-switched data received from applications 1 and 2 and thepacket-switched data received from application 3 into LAC frames whichare transmitted via the common traffic channel to the LAC unit 92. TheLAC unit 92 separates the circuit-switched data from the packet-switcheddata. The packet-switched data is transmitted further to the packet datanode PDN, which is connected to the packet data network. Thecircuit-switched data is transmitted to the RLP unit 93. Theinterworking function IWF of the mobile services switching centre MSCcomprises a corresponding RLP unit 94. A common traffic channel is setup between the units 93 and 94 and an RLP link comprising virtualchannels (two channels in this case) has been established between theunits according to the principles illustrated in FIGS. 4 to 6. The RLPunit 93 packs the circuit-switched data received from the LAC unit 92into RLP frames which are transmitted to the RLP unit 94. The RLP unit94 separates the data of each circuit-switched call or connection fromthe RLP frames and supplies them to a switching unit 95. The switchingunit 95 connects the data of each call selectively to a rate adaptationfunction RA 96, modem 97 or telefax unit 98. The RLP unit 94, switchingunit 95 and units 96 to 98 are preferably similar to the units 52, 53,54, 55 and 56 of FIG. 4. Data transmission in the opposite direction IWFIWU-MS is substantially similar to the data transmission describedabove.

FIG. 11 illustrates transmission of circuit-switched and packet-switched calls according to the invention in a pure third generationmobile communication system. The mobile station MS is similar to thatillustrated in FIG. 10. On the network side the radio access system isconnected to a third generation mobile services switching centre MSC,which comprises an LAC unit 100, rate adaptation function RA 101, modem102, telefax unit 103 and packet data node PDN 104. The LAC unit 100 issubstantially similar to the LAC unit 92 of FIG. 10. According to theinventive idea, a common traffic-channel and LAC link comprising virtualchannels are established between the units 91 and 100. The LAC 91 packsthe circuit-switched and packet-switched data transmitted by theapplications 1, 2 and 3 into LAC frames, which are then transmitted tothe LAC unit 100 via the common traffic channel. The LAC unit 100separates circuit-switched data from the packet-switched data. Thepacket-switched data is supplied to a packet data node PDN 104 whichtransmits the packet data to the packet network. The circuit-switcheddata is supplied selectively (depending on the service the callrequires) to units 101, 102 and 103 which are connected to a PSTN/ISDNnetwork. The LAC unit 100 may also be connected to an ATN network.

FIG. 12 illustrates an approach which is more integrated than that ofFIGS. 9 and 10. In this approach parts of the third generation system,such as the LAC protocol 200, have been embedded in the MC/IWF of thesecond generation. The packet data node PDN may also be integrated intothe IWF. The add-on unit IWU-B is responsible for physical applicationsof the traffic channel (e.g. ATM/ISDN primary rate), any transparentrate adaptations and signalling adaptations. In the case of FIG. 12 onecommon traffic channel is established between the mobile station MS andthe interworking function MSC/IWF. The function of the traffic channelis similar to that in a pure third generation mobile communicationsystem, which was described with reference to FIG. 11.

FIG. 13 illustrates a mobile services switching centre and an IWF poolwhich may be used in the present invention. The transmission channels tothe base station system are connected to one side of the group switchGSW. The transmission channels to the PSTN/ISDN networks are connectedto the other side of the GSW. The IWF pool 110 comprises a number ofRLP/LAC units 52, switching unit 53, number of rate adaptation units RA54, number of modem units 55 and number of telefax units 56. Theswitching unit 53 can selectively switch any RLP/LAC unit to any one ofthe units 54, 55 and 56 (or to more than one unit). The IWF pool alsocomprises a switching unit 111 for switching any one (or any ones) ofthe units 54, 55 and 56 selectively to the transmission channel(transmission channels) to the PSTN/ISDN network. Thus the integratedIWF pool can offer the requested service to any combination of variouscalls. Such a pool separates the virtual channels of simultaneous callsinto physical outgoing transmission channels, each of which can use e.g.a modem, telefax function or ISDN rate adaptation function in the pool110. The network allocates such integrated IWF pool resource 110 when amobile station MS having a multiple call capability sets up the firstcall. Since the mobile services switching centre may also comprisesimple IWF pools which contain only modems, UDI adapters, etc., the callset-up signalling must indicate that the MS has a multiple callcapability. This indication may be included in the BCIE element, as wasexplained above.

In the above-described preferred embodiments of the invention thedifferent calls or connections had a common LAC/RLP protocol inside ofwhich logical channels were established. Alternatively, a separateLAC/RLP protocol (entity) which forms a logical channel of its own viathe common traffic channel can be established for each connection orcall, or for a group of two or more calls or connections. In that casethe LAC/RLP frames belonging to different LAC/RLP entities can bedistinguished from one another by means of the VCI identifier of FIG. 5,for example. Equipment configurations and functions can otherwise beimplemented as was described above in connection with preferredembodiments, except that the RLP/LAC units process parallelly severalRLP/LAC frames.

The invention has been described above by means of preferredembodiments. It should be noted that there are alternative solutions andvariations which are obvious to a person skilled in the art and can beimplemented without deviating from the scope and spirit of the appendedclaims.

1-30. (canceled)
 31. A method of producing two or more simultaneous datacalls for one mobile station in a mobile communication system, themethod comprising: assigning only one common traffic channel to two ormore simultaneous mobile communication network calls of the mobilestation, and sharing the capacity of the common traffic channel betweenthe simultaneous calls, negotiating between the mobile station and amobile communication network about the channel capacity needed for eachcall or connection, and adjusting dynamically the capacity of the commontraffic channel.
 32. A method of producing two or more simultaneous datacalls for one mobile station in a mobile communication system, themethod comprising: assigning only one common traffic channel to two ormore simultaneous mobile communication network calls of the mobilestation, sharing the capacity of the common traffic channel between thesimultaneous calls, negotiating between the mobile station and thenetwork about the channel capacity needed for each call or connection,adjusting the capacity of said common traffic channel dynamically by oneor more of: changing the number of the allocated subchannels in thetraffic channel; changing channel coding; and changing the ratio of chiprate to data rate in the code division multiple access system.
 33. Amethod according to claim 32, comprising: assigning said common trafficchannel to the mobile station when the first call or calls are set up,increasing the capacity of the common traffic channel or reallocatingthe allocated capacity when a new call, or a new connection of an oldcall, is added to the traffic channel, decreasing the capacity of thecommon traffic channel or reallocating the allocated capacity when acall or a connection of a call is cleared from the traffic channel, andreleasing the common traffic channel after the last call has beencleared.
 34. A method according to claim 31, wherein the type of atleast one of the calls is one of the following: a pure non-transparentcall; a pure transparent call; a call comprising at least onenon-transparent connection and at least one transparent connection; anda packet-switched call.
 35. A method of producing two or moresimultaneous data calls for one mobile station in a mobile communicationsystem, the method comprising: assigning only one common traffic channelto two or more simultaneous mobile communication network calls of themobile station, sharing the capacity of the common traffic channelbetween the simultaneous calls, negotiating between the mobile stationand the network about the channel capacity needed for each call orconnection, establishing one radio link protocol link or link accesscontrol protocol link over the traffic channel between the mobilestation and an interworking function, establishing a logical channel foreach call or each connection of each call inside said one radio linkprotocol link or link access control protocol link, and transmitting theuser data of each call or each connection of each call via therespective logical channel.
 36. A method of producing two or moresimultaneous data calls for one mobile station in a mobile communicationsystem, the method comprising: assigning only one common traffic channelto two or more simultaneous mobile communication network calls of themobile station, sharing the capacity of the common traffic channelbetween the simultaneous calls, negotiating between the mobile stationand the network about the channel capacity needed for each call orconnection, establishing a dedicated radio link protocol link or a linkaccess control protocol link for each call or each connection over thetraffic channel between the mobile station and the interworkingfunction, and transmitting user data of each call or connection via thelogical channel established by the respective radio link protocol linkor link access control protocol link.
 37. A method of producing two ormore simultaneous data calls for one mobile station in a mobilecommunication system, the method comprising: assigning only one commontraffic channel to two or more simultaneous mobile communication networkcalls of the mobile station, sharing the capacity of the common trafficchannel between the simultaneous calls, negotiating between the mobilestation and the network about the channel capacity needed for each callor connection, establishing one radio link protocol link or link accesscontrol protocol link over the common traffic channel between the mobilestation and the interworking function, and transmitting data packets ofa packet-switched call either interleaved with the protocol frames ofthe radio link protocol link or the link access control protocol link orencapsulated in the protocol frames.
 38. A method of producing two ormore simultaneous data calls for one mobile station in a mobilecommunication system, the method comprising: assigning only one commontraffic channel to two or more simultaneous mobile communication networkcalls of the mobile station, sharing the capacity of the common trafficchannel between the simultaneous calls, negotiating between the mobilestation and the network about the channel capacity needed for each callor connection, establishing a radio link protocol link or a link accesscontrol protocol link for each call or each connection over the commontraffic channel between the mobile station and the interworkingfunction, and transmitting the data packets of a packet-switched calleither interleaved with the protocol frames of the radio link protocollink or the link access control protocol link or encapsulated in theprotocol frames.
 39. A method according to claim 31, comprising:detecting that the mobile communication network is temporarily unable toallocate more transmission capacity or the required transmissioncapacity to the common traffic channel when a new call or connection isestablished, reallocating the available capacity of the common trafficchannel to the calls, and allocating the requested capacity to thecommon traffic channel later when capacity becomes available in thenetwork.
 40. A method according to claim 31, comprising: monitoring thetraffic of at least one call or connection on the traffic channel,detecting that there is temporarily no traffic in said one call orconnection, and using the temporarily unused resources for the trafficof at least one other call or connection in the common traffic channel.41. A method according to claim 40, comprising: detecting that theinformation flow of the transparent call or connection contains a filleraccording to the protocol used, such as flags or control frames,deleting said filler from the transparent information flow at thetransmitting end, transmitting frames or packets of at least onenon-transparent or packet-switched connection via the traffic channel inplace of said filler, and returning said filler to the receivedinformation flow in the receiver before transmitting it further.
 42. Amobile station which comprises: means for producing two or moresimultaneous data calls for one mobile station in a mobile communicationsystem, said means comprising: means for sharing the capacity of onecommon traffic channel between two or more simultaneous mobilecommunication network calls, means for negotiating between the mobilestation and the network about the channel capacity needed for each callor connection, and means for adjusting the capacity of said commontraffic channel dynamically.
 43. A mobile station according to claim 42,comprising means for establishing a separate subchannel for each call oreach connection of each call in said common traffic channel.
 44. Amobile station comprising: means for producing two or more simultaneousdata calls for one mobile station in a mobile communication system, saidmeans comprising means for sharing the capacity of one common trafficchannel between two or more simultaneous mobile communication networkcalls between, means for negotiating between the mobile station and thenetwork about the channel capacity needed for each call or connection,means for establishing one radio link protocol link or link accesscontrol protocol link over the common traffic channel between the mobilestation and the interworking function, means for establishing a logicallink for each call or each connection of each call inside said one radiolink protocol link or link access control protocol link, means fortransmitting user data of each call or each connection of a call via therespective logical link, and means for adjusting the capacity of saidcommon traffic channel dynamically.
 45. A mobile station comprising:means for sharing the capacity of one common traffic channel between twoor more simultaneous mobile communication network calls, means fornegotiating with a network about the channel capacity needed for eachcall or connection, means for establishing a radio link protocol link orlink access control protocol link for each call or each connection overthe traffic channel between the mobile station and an interworkingfunction, and means for transmitting the user data of each call or eachconnection of each call via the respective logical link established bythe radio link protocol link or link access control protocol link.
 46. Amobile station, comprising: means for sharing the capacity of one commontraffic channel between two or more simultaneous mobile communicationnetwork calls, means for negotiating with a network about the channelcapacity needed for each call or connection, means for establishing oneradio link protocol link or link access control protocol link over thecommon traffic channel between the mobile station and an interworkingfunction, means for establishing a logical link for each call or eachconnection of each call inside said one radio link protocol link or linkaccess control protocol link, means for transmitting user data of eachcall or each connection of a call via the respective logical link, andmeans for transmitting data packets of a packet-switched call eitherinterleaved with the protocol frames of the radio link protocol or linkaccess control protocol or encapsulated in the protocol frames.
 47. Amobile communication network which comprises means for producing two ormore simultaneous calls for a mobile station, said means comprising:means for establishing one traffic channel of the mobile communicationnetwork for two or more mobile communication network calls, means forsharing the capacity of said common traffic channel between saidsimultaneous calls, means for negotiating between the mobile station anda network about the channel capacity needed for each call or connection,and means adjusting dynamically the capacity of the common trafficchannel.
 48. A mobile communication network comprising: means forestablishing one traffic channel of the mobile communication network fortwo or more simultaneous mobile communication network calls of a mobilestation, means for sharing the capacity of said common traffic channelbetween said simultaneous calls, means for negotiating between themobile station and a network about the channel capacity needed for eachcall or connection, and means for adjusting the capacity of said commontraffic channel dynamically.
 49. A mobile communication networkaccording to claim 47, comprising means for establishing a separatesubchannel for each call or each connection of each call in said trafficchannel.
 50. A mobile communication network according to claim 49,comprising: means for establishing one radio link protocol link or linkaccess control protocol link over the traffic channel between the mobilestation and the interworking function, means for establishing a logicallink for each call or each connection of each call inside said radiolink protocol link or link access control protocol link, and means fortransmitting the user data of each call or each connection of each callvia the respective logical link.
 51. A mobile communication networkaccording to claim 49, comprising: means for establishing a radio linkprotocol link or link access control protocol link for each call or eachconnection over the traffic channel between the mobile station and theinterworking function, and means for transmitting the user data of eachcall or each connection of a call via the respective logical linkestablished by the radio link protocol link or link access controlprotocol link.
 52. A mobile communication network according to claim 47,comprising: means for assigning said common traffic channel to themobile station when the first call or calls are set up, means forincreasing the capacity of the common traffic channel or reallocatingthe allocated capacity when a new call, or a new connection of an oldcall, is added to the common traffic channel, means for decreasing thecapacity of the common traffic channel or redistributing the allocatedcapacity when a call or a connection of a call is cleared from thecommon traffic channel, and means for releasing the common trafficchannel after the last call has been cleared.
 53. A mobile communicationnetwork according to claim 47, wherein the type of at least one of thecalls is one of the following: a pure non-transparent call; a puretransparent call; a call comprising two or more connections.
 54. Amobile communication network according to claim 47, comprising: meansfor detecting that the mobile communication network is temporarilyunable to allocate more transmission capacity or the required amount oftransmission capacity to the traffic channel when a new call orconnection is set up, means for reallocating the available capacity ofthe common traffic channel to the calls, and means for allocating therequested capacity to the traffic channel later when capacity becomesavailable in the network.
 55. A mobile communication network accordingto claim 47, wherein the mobile communication network is configured tomonitor the traffic of at least one call or connection on the trafficchannel and to use the temporarily unused resources for the traffic ofat least one other call or connection of the same traffic channel whenit is detected that there is temporarily no traffic in said at least onecall or connection.
 56. A mobile communication network according toclaim 55, comprising: means for detecting that the information flow of atransparent call or connection contains a filler according to theprotocol used, such as flags or control frames, means for deleting saidfiller from the transparent information flow at the transmitting end,means for transmitting frames or packets of at least one non-transparentor packet-switched connection via the common traffic channel instead ofsaid filler, and means for returning said filler to the receivedtransparent information flow in the receiver before the transparentinformation is transmitted further.
 57. A mobile station comprising:means for producing two or more simultaneous mobile communicationnetwork data calls for the mobile station in a mobile communicationsystem, means for sharing the capacity of one common traffic channelassigned to two or more simultaneous calls between said simultaneouscalls, means for negotiating with network about the channel capacityneeded for each call or connection, means for negotiating with a networkabout the use or support of the common traffic channel, and means foradjusting the capacity of said common traffic channel dynamically.
 58. Amobile station according to claim 57, wherein at least one of the two ormore simultaneous calls being a packet data call.
 59. A method ofproducing two or more simultaneous data calls for one mobile station ina mobile communication system, the method comprising: assigning only onecommon traffic channel to two or more simultaneous mobile communicationnetwork calls of the mobile station, sharing the capacity of the commontraffic channel between the simultaneous calls, negotiating between themobile station and a network about the channel capacity needed for eachcall or connection. negotiating between the mobile station and a networkabout the use or support of the common traffic channel, and adjustingdynamically the capacity of the common traffic channel.
 60. A methodaccording to claim 59, wherein at least one of the two or moresimultaneous calls being a packet data call.
 61. A method of producingtwo or more simultaneous data calls for one mobile station in a mobilecommunication system, the method comprising: assigning only one commontraffic channel to two or more simultaneous mobile communication networkcalls of the mobile station, sharing the capacity of the common trafficchannel between the simultaneous calls, negotiating between the mobilestation and a network about the channel capacity needed for each call orconnection, and adjusting dynamically the capacity of the common trafficchannel.
 62. A network element for a mobile communication network,comprising: means for establishing one traffic channel of the mobilecommunication network for two or more simultaneous mobile communicationnetwork calls of a mobile station, means for sharing the capacity ofsaid common traffic channel between said simultaneous calls, means fornegotiating with the mobile station about the channel capacity neededfor each call or connection, and means adjusting dynamically thecapacity of the common traffic channel.
 63. A network element for amobile communication network, comprising: means for establishing onetraffic channel of the mobile communication network for two or moresimultaneous mobile communication network calls of a mobile station,means for sharing the capacity of said common traffic channel betweensaid simultaneous calls, means for negotiating with the mobile stationabout the channel capacity needed for each call or connection, means fornegotiating with the mobile network about the use or support of thecommon traffic channel, and means adjusting dynamically the capacity ofthe common traffic channel.
 64. A network element for a mobilecommunication network, comprising: means for establishing one trafficchannel of the mobile communication network for two or more simultaneousmobile communication network calls of a mobile station, means forsharing the capacity of said common traffic channel between saidsimultaneous calls, means for adjusting dynamically the capacity of thecommon traffic channel according to the required channel capacitydefined by means of negotiation between the mobile station and thenetwork for each call or each connection of each call, means forestablishing a separate subchannel for each call or each connection ofeach call in said traffic channel means for establishing one radio linkprotocol link or link access control protocol link over the trafficchannel between the mobile station and the interworking function, meansfor establishing a logical link for each call or each connection of eachcall inside said radio link protocol link or link access controlprotocol link, and means for transmitting the user data of each call oreach connection of each call via the respective logical link bytransmitting the data packets of a packet-switched call interleaved withthe protocol frames of the radio link protocol or link access controlprotocol or encapsulated in the protocol frames.